GB2339729A - A narrow boat with longitudinal channel forming fins - Google Patents

Description

2339729 A NARROW BOAT The present invention relates to a narrow boat.

Traditionally, narrow boats are flat bottomed boats which, due to their length and the proximity of the propeller to the water surface, have had poor power output. Water close to the surface is more susceptible to aeration which decreases the density of the water and consequently decreases the propeller drive. It is one of the objects of the present invention to overcome these problems.

According to the present invention there is provided a narrow boat comprising a hull with a pair of underwater fins defining a longitudinal channel, the channel being located forward of the propeller.

Advantageously, by locating the pair of fins forward of the propeller, water is channelled through the fins before reaching the propeller thus excluding surface water from the channel and in this manner there is a reduction in the level of aeration in the water reaching the propeller which improves propeller efficiency.

Preferably, a second pair of fins, defining a further longitudinal channel, is located rearward of the first pair with one fin located on either side of the propeller.

Advantageously, by having one fin on either side of the propeller the amount of aerated water from the surface entering the propeller area is further reduced.

Preferably, the first pair of fins are spaced closer together than the second pair so that channelled water from the first pair fans out to enter the area defined by the second pair. Advantageously, in reverse, the water travelling towards the bow of the boat from between the second pair of fins generally fans outside the first pair towards the surface and reduces aerated water going under the boat, thus improving steerage and control during reversal.

Preferably, each pair of fins is parallel and co-extensive.

Preferably, the keel section forms a ridge along the centre of the hull and together with the first pair of fins located either side of the keel forms two longitudinal channels for the water. Preferably, the stem end of the first pair of fins is spaced forward of the forward end of the second pair of fins. Preferably, the stem end of the keel terminates astern the forward end of the 15 second pair of fins, preferably, at the start of a concave propeller cavity.

Preferably, the stem section of the hull between the second pair of fins and above the propeller is concave to further improve the channelling of water through the propeller area in the forward direction.

Preferably, the stern of the boat is fitted with a flap located astern the propeller which may be raised into an above the waterline or lowered into a below the water line position.

Advantageously, the flap has a two fold function. In the raised position, the flap is located on or just above the surface and has a calming effect on the surface of the water, thus reducing turbulence at the rear of the boat. The reduction in turbulence provides a key environmental improvement for narrow -3 waterways where bank erosion due to wash is a significant problem. In the lowered position, the flap reduces the level of aerated water entering the propeller area during reversal of the narrow boat and improves the stopping distance in a forward direction.

Preferably, the flap is concavely profiled with a raised portion in the centre so that it may be located above the rudder and allow lateral adjustment of the rudder during steering. Preferably, the flap is profiled at its ends in such a manner that in the raised position its lateral ends will pass down into the water to further reduce aeration and so that it will direct water down onto the rudder to increase turning efficiency. Accordingly, the lateral ends may be angled towards the bow section or the flap may be arcuate, being convex on its stern side.

According to a second aspect of the present invention, there is provided a narrow boat with a flap fitted to the stem of the boat which may be raised or lowered in such a manner that in the lowered position it partially impedes the flow of water from the surface into the propeller area during reversal of the boat.

Preferably, the bottom edge of the flap is concavely profiled so that it may be located above the rudder and allow lateral adjustment of the rudder during steering.

Preferably, the flap is profiled at its ends in such a manner that in the raised position its lateral sides will curve down into the water to further reduce aeration and so that it will direct water down onto the rudder to increase turning efficiency. Accordingly, the lateral ends may be angled towards the bow section or the flap may be arcuate, being convex on the stem side thereof.

Preferably, in the lowered position, the flap also impedes the flow of water during forward motion of the boat and this may be utilised to reduce stopping distances. This may be combined with the feature of reducing water aeration for the reverse thrust which increases reverse drive by reducing cavitation.

Thus, the flap may have a two-fold benefit.

Preferably, in either aspect of the present invention, to further reduce aeration, the weed box closing element is formed into a box which fits into and substantially fills the weed box cavity above the propeller and thus causes the cavity to be substantially reduced or blocked completely.

Preferably, the box is made from any suitable material but due to weight considerations fibre glass is preferred.

Preferably, the weed box is profiled along its bottom surface to complement the shape of the surrounding hull and present a substantially uninterrupted surface to water flowing under the hull decreasing power loss through aeration in the weed box cavity.

The flap may be allowed to drift rearwardly to attain the raised position as a result of forward momentum. Preferably, the flap is fitted with a stop so that it does not drift substantially forward of the vertical position. Preferably, the second pair of fins extend downward up to a depth parallel with the lowest point of the propeller blade, more preferably, up to a depth parallel with a point three quarters the distance down the propeller width, most preferably, to a depth substantially level with the centre of the propeller.

The embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:- figure 1 shows an underplan view of a narrow boat hull in accordance with the first aspect of the present invention; figure 2 shows a side elevation of the stern section of a narrow boat in accordance with the present invention; figure 3 shows a cross-sectional view through line C-C of figure 2; figure 4 shows a cross-sectional view through line B-B of figure 2; figure 5 shows a cross-sectional side elevation through the stem section of the narrow boat; figure 6 shows a cross-sectional view through line A-A of figure 2; figure 7 shows a cross-sectional view through line Z of figure 2; and figure 8 shows a section through the mid-ship portion of the boat revealing the 25 chine and keel arrangement.

Referring to figure 1, the underplan view shows aspects of the narrow boat hull design. The hull 2 includes a keel 4 running along the centre of the hull.

The hull rises gently from the keel section as far as the chine 6 whereupon it rises more steeply to terminate in a further angle 8 before rising almost vertically to the top of the hull. A pair of longitudinal and coextensive forward fins (10a, 10b) depend downwardly from the base section 5 of the hull. The fins are parallel with and located on either side of the keel and extend from the mid-ships before terminating in the stem section of the boat. A second pair of longitudinal and parallel fins 12, forming a wider channel than the forward fins, extend forwardly from the rear of the boat before terminating short of the stem ends of the forward fins 10. The keel terminates in the stern section of the boat astem the stem ends of the front fins 10 and slightly astem of the front ends of the rear fins 12.

In use, during forward movement of the narrow boat, water is channelled on either side of the keel 4 and within the longitudinal channel formed by the front fins 10. The front fins reduce the level of aeration or cavitation in the water by preventing surface water entering the channel so that the water emerging from the stern ends of the front fins 10 has reduced cavitation before it fans out into the wider channel formed by the rear fins 12 to provide water with reduced cavitation around the propeller located between the rear fins 12. When the narrow boat is travelling in a reverse direction, the wider spacing between the rear fins compared with the forward fins and the longitudinal gap between the pairs of fins allows the escape of aerated water to the surface which reduces the level of aeration or cavitation in water going under the boat thus improving steerage and control during reversal of the boat. By terminating the keel section astern the front ends of the rear fins 12, the channelled water coming through the channels defined by the front fins is continuously guided into the channel area defined by the rear fins.

Referring to figure 4, it can be seen that the rear fins 12 define the lateral outer limits of a concave cavity 14 in which the propeller is housed. By housing the propeller in such a concave cavity with the rear fins located on the port and starboard side of the cavity, cavitation in the cavity is greatly 5 reduced thus improving propeller drive efficiency.

Referring to figure 2, the keel 4 can be seen to extend as far as the stem cavity 14 in which the propeller 16 is housed, whereas the front ends of the side fins 12 defining the port and starboard sides of the stern cavity 14, terminate just forward of the stem end of the keel 4.

Referring to figure 3, a stem flap 20 is shown mounted above a rearwardly downwardly convexly sloping rudder 22 and substantially co-planar with the rear of the boat 24. The stem flap is designed to be closely spaced from the top of the rudder but to allow free movement thereof to the port and starboard sides. Accordingly, the bottom edge of the stem flap in the vicinity of the rudder 22 is arcuate to allow for the varying height of the sloping rudder in the plane of the rear of the boat 24 between extreme port and starboard positions of the rudder. Referring to figure 5, a cross-section through the rudder shows that it slopes away steeply astern the flap 20 which causes the requirement for the arcuate form of the centre of the flap so that the flap may remain in close proximity to the part of the rudder in the plane of the rear of the boat through the range of the port to starboard movement of the rudder.

Referring to figures 2 and 3, the front fins 10 extend at a substantially constant depth from front to stem ends whereas the rear fins 12 are located at an increasingly greater depth as they pass from the front to the rear of the stern section of the boat 24.

-8 Referring to figure 5, cross-section through the engine, propeller and rudder arrangement is shown. The propeller 16 is mounted on the end of the propeller shaft 30 which is driven by engine 32 about the axis of the shaft 30.

The shaft is housed in a stainless steel stern tube which in turn is housed in an outer lining tube 32. The lining tube 32 is fixed to the skeg 34 and eye bracket 36 with the eye bracket extending from the skeg 34 into the hull where it is securely fixed. The skeg 34 forms an extension to the keel 4 and overlaps with the stern section of the keel to be secured thereto at its front end. The stern end of the skeg secures the bottom end of the stern post 40 which in turn secures the rudder 42 for rotation about the stem post from the port to starboard direction and vice-versa. The rudder extends rearwardly from the stem post with its base edge substantially parallel with the axis of the keel and its upper edge sloping away downwardly in a convex line which is proximate with and follows the profile 42 of the stem cavity 14 located above until it is level with the rear of the boat whereupon it slopes downwardly at a more severe rate until it meets the vertical rear edge of the rudder. In the details shown in figure 5, it can be clearly seen that the rear flap 20 is spaced slightly inwardly from the rear 24 of the boat and depends downwardly from the top of a recess formed in the rear of the boat just above the rudder. The weed box 50 is located above the propeller 16 and has a profiled bottom surface which compliments the surrounding bottom surface of the hull in the stem cavity. Hitherto the weed box cavity has been sealed at the top leaving a recess above the propeller, which eases propeller accessibility once the closure element is removed from the top of the weed box but increases aeration of the water in the propeller area. The use of a fibreglass weed box allows the closing element to have a downwardly dependent box which fills the weed box cavity and is profiled on its base to compliment the surrounding hull area. By designing the weed box in this manner, water flow in the stern cavity area 14 is improved and the possibility of a recessed area above the propeller shaft causing increased cavitation is removed. The securement and securing members of the weed box, propeller, skeg and stem post are in accordance with techniques and designs known to those skilled in the art.

Referring to figure 6, the bottom profile of the hull pod which houses the engine 32 can be clearly seen. From the keel area 4 the pod describes a bulbous convexly profiled section 56 on either side of the keel which extends upwardly to a shallower depth than the rear fins 12 so that a channel is formed between the bulbous portion 56 and the rear fins 12 in the area of the hull on the lateral sides of the engine pod. These channels assist the flow of water in the area around the pod. In addition, the profile of the channel with respect to the rear fins 12 further reduces cavitation in the area.

Referring to figure 7, the forward fins 10 can be shown in section depending downwardly from the bottom of the boat on either side of the keel 4 and effectively forming a channel comprising two part channels between the keel and the fins on either side of the keel.

Referring to figure 8, a section through the hull forward of the front fins 10 is shown. In this area, it can be seen that the hull extends upwardly from the keel at a shallow angle before rising more steeply after the chine angle 6 to meet angle 8 at the base of the sides 60 of the hull.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and -10the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the 20 steps of any method or process so disclosed.

Claims (35)

CIAIMS

1. A narrow boat comprising a hull with a pair of underwater fins defining a longitudinal channel, the channel being located forward of the propeller.

2. A narrow boat according to claim 1, wherein a second pair of fins, defining a further longitudinal channel, is located rearward of the first pair with one fin located on either side of the propeller.

3. A narrow boat according to claim 2, wherein the first pair of fins are spaced closer together than the second pair so that channelled water from the first pair fans out to enter the area defined by the second pair.

4. A narrow boat according to any preceding claim, wherein each pair of fins is parallel and co extensive.

5. A narrow boat according to any preceding claim, wherein the keel section forms a ridge along the centre of the hull and together with the first pair of fins located either side of the keel forms two longitudinal channels for the water.

6. A narrow boat according to any of claims 2-5, wherein the stern end of the first pair of fins is spaced forward of the forward end of the second pair of fins.

7. A narrow boat according to any of claims 2-6, wherein the stern end of the keel terminates astern the forward end of the second pair of fins.

8. A narrow boat according to claim 7, wherein the keel terminates at the start of a concave propeller cavity.

9. A narrow boat according to any of claims 2-8, wherein the stern section of the hull between the second pair of fins and above the propeller is concave to further improve the channelling of water through the propeller area when the boat moves in the forward direction.

10. A narrow boat according to any preceding claim, wherein the stern of the boat is fitted with a flap located astern the propeller which may be raised into an above the water line or lowered into a below the water line position.

11. A narrow boat according to claim 10, wherein the flap is concavely profiled with a raised portion in the centre so that it may be located above the rudder and allow lateral adjustment of the rudder during steering.

12. A narrow boat according to claim 10 or 11, wherein the flap is profiled at its ends in such a manner that in the raised position its lateral ends will pass down into the water to further reduce aeration and so that it will direct water down onto the rudder to increase turning efficiency.

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13. A narrow boat according to any of claims 10-12, wherein the lateral ends are angled towards the bow section.

14. A narrow boat according to any of claims 10-13, wherein the flap is arcuate, being convex on its stern side.

15. A narrow boat with a flap fitted to the stern of the boat which may be raised or lowered in such a manner that in the lowered position it partially impedes the flow of water from the surface into the propeller area during reversal of the boat.

16. A narrow boat according to claim 15, wherein the bottom edge of the flap is concavely profiled so that it may be located above the rudder and allow lateral adjustment of the rudder during steering.

17. A narrow boat according to claims 15 or 16, wherein the flap is profiled at its ends in such a manner that in the raised position its lateral sides will curve down below the surface of the water to further reduce aeration and so that it will direct water down onto 25 the rudder to increase turning efficiency.

18. A narrow boat according to any of claims 15-17, wherein the lateral ends are angled towards the bow section when the flap is in the vertical position.

19. A narrow boat according to any of claims 15-18, wherein the flap is arcuate, being convex on the stern side thereof.

20. A narrow boat according to any of claims 15-19, wherein in the lowered position, the flap also impedes the flow of water during forward motion of the boat.

21. A narrow boat according to any preceding claim, wherein to further reduce aeration, the weedbox closing element is formed into a box which fits into and substantially fills the weed box cavity above the propeller and thus causes the cavity to be substantially reduced or blocked completely.

22. A narrow boat according to any preceding claim, wherein the weed box is profiled along its bottom is surface to complement the shape of thesurrounding hull and present a substantially uninterrupted surface to water flowing under the hull decreasing power loss through aeration in the weed box cavity.

23. A narrow boat according to any of claims 10-22, wherein the flap is fitted with a stop so that it does not drift substantially forward of the vertical position.

24. A narrow boat according to any of claims 10-23, wherein the flap is designed to extend at least partially beneath the water surface and to adopt a substantially vertical position during reversal of the boat.

25. A narrow boat according to any of claims 2-24, wherein the second pair of fins extend downward up to a depth parallel with the lowest point of the propeller blade.

26. A narrow boat according to any of claims 2-25, wherein the second pair of - fins extend to a depth parallel with a point three quarters the distance down the 5 propeller width.

27. A method of producing a mould for a narrow boat comprising the step of:

producing a mould suitable to produce a hull shape according to any of claims 1-26.

28. A method of producing a mould plug for a narrow boat comprising the step of:

producing a plug having at least one surf ace with the features of any one or more of claims 1-26.

29. A method of using a narrow boat according to any of claims 10-26 comprising the step of:

raising the flap or allowing it to be raised for use during forward movement-of the boat.

30. A method of using a narrow boat according to any of claims 10-26 comprising the step of lowering the flap or allowing it to be lowered for use during rearward movement of the boat.

31. A narrow boat as hereinbefore described with reference to the drawings.

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32. A method of using a narrow boat as hereinbefore described with reference to the drawings.

33. A method of reducing cavitation on a narrow boat according to any of claims 10-26, wherein the flap is lowered or allowed to lower for use during rearward movement of the boat.

34. A method of reducing cavitation on a narrow boat according to any of claims 10-26, wherein the flap is raised or allowed to raise for use during forward movement of the boat.

35. A method according to claim 34, wherein the flap is supported in its raised position by the surface water during forward movement of the boat.